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问题 问答题 简答题

为什么采用AlGaAs/GaAs异质结结构制造的双极型晶体管（HBT）具有好的性能？

答案

参考答案：

异质结双极性晶体管的发射极效率主要由禁带宽度差决定，几乎不受掺杂比的限制

单项选择题

大叶性肺炎属于( )

A．化脓性炎症

B．浆液性炎症

C．增生性炎症

D．出血性炎症

E．纤维素性炎症
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单项选择题

The following questions present a sentence, part of which or all of which is underlined. Beneath the sentence, you will find five ways of phrasing the underlined part. The first of these repeats the original; the other four are different. If you think the original is best, choose the first answer; otherwise choose one of the others.

These questions test correctness and effectiveness of expression. In choosing your answer, follow the requirements of standard written English; that is, pay attention to grammar, choice of words, and sentence construction. Choose the answer that produces the most effective sentence; this answer should be clear and exact, without awkwardness, ambiguity, redundancy, or grammatical error.

Four Dynacorp Optimall Omniprocessors were shipped in the fourth quarter, and it brought to 13 the number of these ultra-high-capacity processors shipped during the year.（）

A. and it brought

B. by bringing

C. and brings

D. having brought

E. bringing
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